Robust Split Laser Sensor for Harsh Environment Sensing Applications

C53-24a-271332For long-term CO2 sequestration monitoring, it is important to detect elevated levels of metal contaminants such as Ca, K, Sr, etc., is soil and water as it can provide an early detection of CO2 leakage from geologic carbon storage. Technologies are also needed for direct and in situ measurements of greenhouse gases, CO2 and CH4 for environmental monitoring. For in situ and real-time measurements, we employed a DOE patented split laser measurement technology (SLMT) for laser induced breakdown spectroscopy (LIBS) to measure elemental species (Na, Ca and Sr) and Raman spectroscopy to measure CO2 and CH4 under harsh environmental conditions. A significant part of the effort was devoted to the upgrade of the current SLMT by incorporating innovative packaging and sealing of the sensor head for ruggedness and to withstand the harsh environments anticipated during underwater and downhole sensing applications. We successfully built a compact and sealed prototype split laser that delivered high-energy nanosecond pulses and was able to perform LIBS experiments for species detection of Na, Ca, Sr, Eu, and Yb and obtain limits of detection on the level of 10~25 parts per million in aqueous solutions. Different combinations of spectral analyzers and photon detectors were tested, thereby permitting a study on the relative performance and cost analyses. Raman spectroscopy was also successfully demonstrated to detect dissolved CO2 in water. Based on the promising results obtained during Phase I, we will continue to refine the split laser to further enhance its performance and built three sensors – a LIBS sensor, a NIR Raman sensor, and a NIR cavity enhanced Raman spectroscopy (CERS) sensor, for in situ, standoff monitoring of trace metals and dissolved gases in water and validate its performance using laboratory experiments and field tests deep underground in downhole configuration. The validation of these sensors using field tests will lead to the development of rugged sensors that are capable of field deployment. Further refinement of these rugged sensors will lead to mature products that can be commercialized. The proposed system will support laser induced breakdown spectroscopy (LIBS) and Raman scattering measurements of gases, liquids, and solids. There is a great need in providing an inexpensive and compact measurement device suitable for real-time assessment of air, water, and soil quality, which is highly important to oil and gas exploration companies, landowners, regulatory agencies, municipalities, and any organization measuring emissions and pollutants.